Recent medical research has discovered new differences in susceptibility to disease between blacks and whites. A study conducted by the Cincinnati Children’s Hospital Medical Center shows that African-American children, who suffer disproportionately from tobacco-related illnesses, have significantly higher levels of cotinine, a substance produced in the breakdown of nicotine, even though their parents report less exposure to tobacco smoke.

“Racial Differences in Exposure to Environmental Tobacco Smoke among Children,” which appears in the March 2005 issue of Environmental Health Perspectives, found that, after taking environmental factors into account, black children with asthma had markedly higher levels of cotinine than did asthmatic white children, implying an inherited basis for African-Americans’ vulnerability to tobacco-induced illnesses. A second study of differences between whites and blacks in risk and progression of multiple sclerosis (“Clinical Characteristics of African Americans vs. Caucasian Americans with Multiple Sclerosis,” Neurology, December 14, 2004) has found that while blacks are less susceptible to MS than whites, the disease develops more quickly in blacks, and is more likely to be accompanied by lessened mobility, or by symptoms restricted to the optic nerve and spinal cord. While the study did not attempt to distinguish between hereditary and environmental factors, it has laid a basis for follow-up studies planned to determine the role of genetic factors in determining racial differences in multiple sclerosis.

Source: The Occidental Herald

Racial Differences in MS Explored

by John C. Martin

A new study has found distinct racial differences in the risk and progression of multiple sclerosis (MS).1 The research, headed by Bruce Cree, MD, PhD, at the University of California at San Francisco, compared characteristics of MS in African-American patients versus Caucasians.

Disease Distinctions Uncovered

Cree's group found that African-Americans tend to experience a more aggressive form of the illness, were at higher risk for developing difficulties related to mobility, and were more likely to develop MS at a later age than whites. However, the study also found that African-Americans were more likely diagnosed earlier than Caucasians.
"The median time to diagnosis was 1 year after symptom onset in African-American subjects and 2 years after symptom onset in Caucasian subjects," wrote Cree and his fellow investigators.

A consortium of researchers retrospectively examined the medical records of 375 African-American patients compared with 427 Caucasian patients with the disease, specifically searching for various features of MS. They collected clinical information and DNA evidence from both sets of patients and their families for this study. The study also uncovered that blacks were at higher risk of developing MS-related symptoms restricted to the optic nerve and spinal cord.

According to the National Multiple Sclerosis Society, which co-funded this study, MS is relatively rare in African Americans. The risk of the disease to blacks is about half what is in whites. Such differences may provide clues to the genetic origins behind this disease, the society noted.

A More Aggressive Pathology in Blacks

But when African-Americans are diagnosed, the clinical course of the disease is much more aggressive, the study found, progressing to the point at which a cane is needed to walk within 16 years, on average. This same progression takes about 22 years, on average, in whites, the study researchers learned. All taken, blacks are over 1.5 times more likely to require assistance to walk than whites, after taking other factors like differences in medications taken into account, Cree and his team noted.

Other Key Differences

Blacks also tend to contract the disease about 2.5 years later than in whites, yet African-Americans tend to be diagnosed much more quickly. African-Americans also tended to present with symptoms from more than one area of the body, such as the brain and spinal cord, than whites, the study found. Opticospinal MS, a form of the disease restricted to the optic nerve and spinal cord, occurred in nearly 17 percent of the African-American population studied versus about 8 percent of Caucasians. African-Americans also faced a higher risk of developing transverse myelitis, an acute attack in which the spinal cord loses its ability to transmit nerve impulses back and forth.

Still, this suggests that African-Americans tend to lose their normal mobility faster over time. The reason for this is due in part to their older age at the onset of the disease, and may also be due to the higher incidence of transverse myelitis, Cree and his team surmised. This condition causes paralysis and numbness in the legs and trunk below the level of inflammation.

The researchers also checked to see if there were differences in access to care or in therapy prescribing and use between the two groups, but found that there was no significant delay from onset of symptoms to diagnosis in either group. Either group was about equally likely to receive disease-modifying medications for MS, as well.

Study Drawbacks

There were limits to this study, Cree's team underscored. The retrospective nature of the analysis (reviewing medical records) meant that aspects such as environmental or socioeconomic factors that might affect the results were not considered. Taking these factors into account might have changed the findings, they stressed.

However, the research team is planning a prospective study, in which patients with MS will be followed for a certain period of time, in hopes of confirming these findings. The investigators also want to determine if certain genetic factors play a key role in the distinctive nature of MS between African-Americans and Caucasians.


About the Author: John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include coverage of health news for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.
1. Cree BA, Khan O, Bourdette D et al. Clinical characteristics of African Americans vs Caucasian Americans with multiple sclerosis. Neurology 2004 Dec 14;63(11):2039-45.